Recent large-scale sequencing efforts have revealed prevalent mutations in splicing factor-encoded genes in bone marrow failure diseases, such as myelodysplastic syndromes (MDS) and related disorders. In particular, mutations in the splicing factor SRSF2 were significantly associated with mutations of RUNX1, a transcription factor with an established role in various blood cell disorders. These findings suggest a critical role of thes factors in blood cell pathology, likely through their synergistic effects in regulated gene expression, and potentiate the development of new therapeutics against specific types of bone marrow failure disorders. The goal of this proposal is to establish the causal role of SRSF2 mutations and their genetic interactions with RUNX1 in bone marrow disorders. Our labs have been systematically pursuing the biological function and regulatory mechanisms of RUNX1 (Zhang lab) and SRSF2 (Fu lab) for many years. Recently, our research has led to novel insights into the mechanism of these genes in regulated gene expression. We have an established collaborative record, and our combined expertise is ideally suited to pursue the disease mechanism and develop novel therapeutic strategies through a concerted effort. Therefore, we propose to join forces to attack the problem under the following specific aims: 1) Establish causal mutations of SRSF2 and RUNX1 in MDS. We hypothesize that the mutations synergistically promote abnormal blood cell proliferation and development. 2) Understand the impact of the Proline 95 mutations on the functional properties of SRSF2. We hypothesize that MDS-associated mutations in SRSF2 may have altered the function of SRSF2 to affect specific splicing and/or transcription events that are critical for the development of blood cells. 3) Defin critical molecular pathways underlying the disease phenotype. We hypothesize that mutations in these genes cause specific changes in regulated gene expression to favor disease development. We propose to define the altered molecular pathways using both cells isolated from animal models and human patient samples. In sum, we design the research through testing key hypotheses by using the latest genetic and genomic approaches. This proposal takes full advantage of our many years of effort and experience in basic and translational research. The studies are expected to provide valuable insights into the pathology of SRSF2 and RUNX1 mutation related bone marrow failure diseases, which will eventually benefit patients by facilitating the development of pathway directed chemical screening strategies.